Article of Footwear With Lightweight Sole Assembly

ABSTRACT

A sole assembly for an article of footwear has a first portion having a lower ground engaging surface, an upper surface, and a recess formed in the upper surface. A second portion is seated in the recess in the first portion and has an upper surface. The second portion is formed from a first foam material prepared by a reaction product of a composition having about 10 to about 100 phr of a hydrogenated copolymer and about 10 to about 90 phr of a copolymer of ethlylene and an alpha olefin, the alpha olefin having up to 20 carbon atoms. The first foam material has a hardness of 25 to 45 Asker C and a density of less than 0.18 g/cm3.

This application is a continuation application of Ser. No. 14/314,211filed Jun. 25, 2014, which is a divisional application of Ser. No.13/045,571 filed Mar. 11, 2011, now U.S. Pat. No. 8,809,408, which is adivisional of Ser. No. 11/752,348, filed May 23, 2007, now U.S. Pat. No.7,941,938, issued May 17, 2011, which application claims priority toprovisional application Ser. No. 60/808,551, filed May 26, 2006,expired, said prior applications being entirely incorporated herein byreference.

BACKGROUND

A conventional article of athletic footwear includes two primaryelements, an upper and a sole structure. The upper provides a coveringfor the foot that securely receives and positions the foot with respectto the sole structure. In addition, the upper may have a configurationthat protects the foot and provides ventilation, thereby cooling thefoot and removing perspiration. The sole structure is secured to a lowerportion of the upper and is generally positioned between the foot andthe ground. In addition to attenuating ground reaction forces (i.e.,imparting cushioning), the sole structure may provide traction andcontrol foot motions, such as pronation. Accordingly, the upper and thesole structure operate cooperatively to provide a comfortable structurethat is suited for a variety of ambulatory activities, such as walkingand running.

The sole structure of athletic footwear generally exhibits a layeredconfiguration that may include a comfort-enhancing insole, a resilientmidsole formed from a polymer foam material, and a ground-contactingoutsole that provides both abrasion-resistance and traction. The midsoleis the primary sole structure element that imparts cushioning andcontrols foot motions. Suitable polymer foam materials for the midsoleinclude ethylvinylacetate or polyurethane, which compress resilientlyunder an applied load to attenuate ground reaction forces created by theimpacts of running and jumping.

Conventional polymer foam materials are resiliently compressible, inpart, due to the inclusion of a plurality of open or closed cells thatdefine an inner volume substantially displaced by gas. The polymer foammaterials of the midsole may also absorb energy when compressed duringambulatory activities. The compression of the foam is affected byhysteresis loss, and deflection of such systems is affected by thevolume of the compressed mass of the midsole.

There are several types of materials used to prepare midsoles. Theseinclude ethylene vinyl acetate (EVA), materials containing EVA, forexample Phylon and Phylite, polyurethane and materials containingpolyurethane.

Ethylene vinyl acetate (EVA) is soft, light, and flexible. It is theleast expensive midsole material and is often used in entry-level shoes.Midsoles are cut and shaped from flat sheets of EVA foam. EVA willcompress and become flat over time as the air trapped within the foam issqueezed out. Once EVA is compacted, it does not return to its originalshape and no longer provides cushioning. EVA compresses faster thanother midsole materials.

Phylon is made of EVA foam pellets, slabs, or sheets that arecompressed, heat expanded, and then cooled in a mold. Compression-moldedPhylon midsoles can be sculpted into a variety of designs that can beidentified by their fine wrinkles. Phylon is very lightweight,low-profile, and responsive.

Phylite is an injection-molded unit made of a combination of 60% Phylonand 40% rubber. Phylite is lighter than rubber, but heavier than Phylonand functions as both midsole and outsole. By eliminating a separatemidsole and outsole the weight of the shoe is greatly reduced andflexibility is increased.

Polyurethane is a dense, durable, and stable midsole material.Typically, polyurethane is poured into a mold to create a firm midsolethat provides maximum protection from impact. Polyurethane is identifiedby its smooth rubbery feel and tendency to turn yellow with age.Polyurethane is the heaviest midsole material, but it is also the mostdurable

It would be desirable to provide a footwear cushioning system thatreduces or overcomes some or all of the difficulties inherent in priorknown devices. Particular objects and advantages will be apparent tothose skilled in the art, that is, those who are knowledgeable orexperienced in this field of technology, in view of the followingdisclosure of the invention and detailed description of certainembodiments.

SUMMARY

The principles of the invention may be used to advantage to provide anarticle of footwear having a lightweight sole assembly. This lightweightsole assembly provides footwear that is significantly lighter than otherfootwear, providing advantages to athletes in running and basketball,for example.

In accordance with a first aspect, a foam material is prepared from areaction product of about 10 to about 100 phr hydrogenated ornon-hydrogenated acrylonitrile butadiene copolymer, 0 to about 40 phrmodified hydrogenated acrylonitrile butadiene copolymer, and 0 to about90 phr alpha olefin copolymer.

In accordance with another aspect, a foam material is used to prepare anarticle of footwear. The article of footwear has an upper; and a soleassembly secured to the upper, and at least a portion of the soleassembly is prepared from the foam material.

In accordance with another aspect, a foam material has a density lessthan 0.25 g/cc³ and a resiliency greater than 40.

Substantial advantage is achieved by providing an article of footwearwith a lightweight sole assembly. In particular, certain embodimentsallow an article of footwear to be highly responsive while reducing theweight of the footwear, thereby improving performance and comfort.

These and additional features and advantages disclosed here will befurther understood from the following detailed disclosure of certainembodiments.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevation view of an article of footwear with a lightweightsole assembly in accordance with an aspect of the invention.

FIG. 2 is an exploded view of the sole assembly of the article offootwear of FIG. 1.

FIG. 3 is a plan view of the bottom of the sole assembly of FIG. 1.

FIG. 4 is a bottom view of an insert of the sole assembly of FIG. 2

FIG. 5 is a top view of the sole assembly of FIG. 2.

FIGS. 6a-6f are comparative results from tests of sole assembly ofExample 4.

The figures referred to above are not drawn necessarily to scale andshould be understood to provide a representation of the invention,illustrative of the principles involved. Some features of the article offootwear depicted in the drawings have been enlarged or distortedrelative to others to facilitate explanation and understanding. The samereference numbers are used in the drawings for similar or identicalcomponents and features shown in various alternative embodiments.Articles of footwear as disclosed herein would have configurations andcomponents determined, in part, by the intended application andenvironment in which they are used.

DETAILED DESCRIPTION

(Footwear Description)

Aspects of the invention utilize hydrogenated foams for lightweightmaterial. Further aspects relate to a foamed material with a spongy feel(like walking on the Moon or marshmallows). Further aspects of theinvention are directed to light weight, high bouncing feel lunar shoes.

The present invention may be embodied in various forms.

The footwear may be any suitable footwear such as running shoes orbasketball shoes where light weight, high bouncing, properties aredesired. Running shoes, for example, can be made that are less than halfthe weight of other conventional running shoes.

One embodiment of an article of footwear 10 is shown in FIG. 1. Footwear10 includes an upper 12 and a sole assembly 14 secured to upper 12. Soleassembly 14 may be secured to upper 12 by adhesive or any other suitablemeans. Footwear 10 has a medial, or inner, side 16 and a lateral, orouter, side 18.

Sole assembly 14, which is generally disposed between the foot of thewearer and the ground, provides attenuation of ground reaction forces(i.e., imparting cushioning), traction, and may control foot motions,such as pronation. As with conventional articles of footwear, soleassembly 14 may include an insole (not shown) located within upper 12.

For purposes of general reference, footwear 10 may be divided into threegeneral portions: a forefoot portion 20, a midfoot portion 22, and aheel portion 24. Portions 20, 22, and 24 are not intended to demarcateprecise areas of footwear 10. Rather, portions 20, 22, and 24 areintended to represent general areas of footwear 10 that provide a frameof reference during the following discussion.

Unless otherwise stated, or otherwise clear from the context below,directional terms used herein, such as rearwardly, forwardly, top,bottom, inwardly, downwardly, upwardly, etc., refer to directionsrelative to footwear 10 itself. Footwear is shown in FIG. 1 to bedisposed substantially horizontally, as it would be positioned on ahorizontal surface when worn by a wearer. However, it is to beappreciated that footwear 10 need not be limited to such an orientation.Thus, in the illustrated embodiment of FIG. 1, rearwardly is toward heelportion 24, that is, to the right as seen in FIG. 1. Naturally,forwardly is toward forefoot portion 20, that is, to the left as seen inFIG. 1, and downwardly is toward the bottom of the page as seen inFIG. 1. Top refers to elements toward the top of the page as seen inFIG. 1, while bottom refers to elements toward the bottom of the page asseen in FIG. 1. Inwardly is toward the center of footwear 10, andoutwardly is toward the outer peripheral edge of footwear 10.

As can be seen in FIG. 2, sole assembly 14 consists of a first portion26 having an upper surface 27 with a recess 28 formed therein. Uppersurface 27 is secured to upper 12 with adhesive or other suitablefastening means. A plurality of substantially horizontal ribs 30 isformed on the exterior of first portion 26. In certain embodiments, ribs30 extend from a central portion of forefoot portion 20 on medial side16 rearwardly along first portion 26, around heel portion 24 andforwardly on lateral side 18 of first portion 26 to a central portion offorefoot portion 20.

First portion 26 provides the external traction surface of sole assembly14. In certain embodiments it is to be appreciated that a separateoutsole component could be secured to the lower surface of first portion26.

Recess 28 extends from heel portion 24 to forefoot portion 20. Incertain embodiments, the rear surface 32 of recess 28 is curved tosubstantially follow the contour of the rear of heel portion 24 and thefront surface 34 of recess 28 extends transversely across first portion26.

An insert 36 is received in recess 28. Insert 36 has a curved rearsurface 38 to mate with curved rear surface 32 of recess 28 and atransverse front surface 40 to mate with transverse front surface 34 ofrecess 28. An upper surface 42 of insert 36 is in contact with andsecured to upper 12 with adhesive or other suitable fastening means.

As seen best in FIG. 3, a ground engaging lower surface 44 of firstportion 26 includes a plurality of projections 46. Each projection 46 issurrounded by a groove 48. A plurality of transverse slots 50 are formedin lower surface 44, extending between adjacent projections 46. Alongitudinal slot 52 extends along lower surface 44 from heel portion 26to forefoot portion 20.

Insert 36 is formed of a very lightweight yet resilient material. Firstportion 26 provides structure and support for insert 36. In certainembodiments, insert 36 is formed of a foam material.

Another embodiment utilizes an insert 60 similar to insert 36 butwherein the insert comprises two types of foam material. A higherdensity foam supports the heel region and a lower density foam supportsthe toe region. For example, as shown in FIG. 4 the insert can be madefrom foam 62 having a density of 0.25 g/cm³ such as Phylon wherein aportion of the foam in the toe region is replaced with foam 64 having adensity less than 0.25 g/cm³. Alternatively, the insert may be preparedfrom a foam having a density less than 0.25 g/cm³ and the heel regioncould be replaced with higher density foam. The shape of the foamportions of the insert may be any suitable shape. For example, the heelregion may be in the form of a wedge to provide additional support forthose athletes that tend to over pronate on the medial side of thefootwear. This type of duel density insert may be particularly useful ina basketball style shoe. FIG. 5 shows insert 60 containing two types ofmaterial 62 and 64, placed in portion 66.

(Introduction to Foam Material)

The foam material used in embodiments described herein has a density ofless than 0.25 g/cc². This, combined with other properties such as aresilience of greater than 40, provides a foam material useful inapplications requiring lightweight foam such as a midsole of footwear.

The foam material is prepared from a mixture of hydrogenated ornon-hydrogenated acrylonitrile-butadiene copolymer; modifiedhydrogenated acrylonitrile-butadiene copolymer; and alpha olefincopolymer. Non-hydrogenated (standard) acrylonitrile-butadiene copolymerprovides lower cost foam than hydrogenated acrylonitrile-butadienecopolymer. The non-hydrogenated acrylonitrile-butadiene copolymergenerally has a higher shrinkage than hydrogenatedacrylonitrile-butadiene copolymer.

After mixing and addition of other optional additives, the mixture isultimately foamed for use as a foamed material. For example, the foammaterial is used as an inner midsole core having a density less thanabout 0.25 g/cm³. This core is surrounded by a more rigid outer shellprepared from, for example but not limited to, EVA, Phylon, andpolyurethane. Moreover, at higher densities (e.g. about 0.30 g/cm³), thefoam material can be used as the entire midsole component or as amidsole/outsole combination component.

The foam material provides the footwear user(s) a perception of softcomfortable cushioning and energy return. This perceived feeling ofcushioning and energy return can be quantified using its physicalproperties, namely high resilience, hardness (e.g. from 20 to 30 Asker Cup to 50 Asker C for certain shoes such as basketball shoes) and lowenergy loss. This foam is not limited to footwear applications, but canalso be used in all sport related equipment where the above mentionedimproved properties are required.

(Foam Material)

The foam material is prepared from a mixture of hydrogenated ornon-hydrogenated acrylonitrile-butadiene copolymer; modifiedhydrogenated acrylonitrile-butadiene copolymer; and alpha olefincopolymer.

Examples of hydrogenated acrylonitrile-butadiene copolymers includeZetpol 2000. Other grades of hydrogenated acrylonitrile-butadienecopolymer can be used with different percentages of polymer saturation.Typically, this copolymer is used in an amount of about 10 to about 100parts per hundred (phr), such as about 30 to about 90 phr, or about 40to about 70 phr.

Non-hydrogenated acrylonitrile-butadiene copolymers can be partially orfully substituted by polybutadiene, styrene butadiene, ethylenepropylene diene terpolymer, chlorosulfonated polyethylene polymers,thermoplastic elastomers (TPE) can also be used to form the mixture ofcopolymers.

Modified hydrogenated acrylonitrile-butadiene copolymers arehydrogenated acrylonitrile-butadiene copolymers are modified withmodifiers such as zinc oxide and zinc diacrylate. Suitable modifiedhydrogenated acrylonitrile-butadiene copolymers include ZCS 2095 (ZeonChemicals). Typically, this copolymer is used in an amount of from 0 toabout 40 phr, such as about 5 to about 40 phr, about 10 to about 30 phr,or about 15 to about 20 phr.

The alpha olefin copolymer includes an ethylene and an alpha olefin, forexample having up to 20 carbon atoms, such as but not limited tocopolymers of ethylene and octene-1, ethylene-methyl acrylate copolymer,and ethylene vinyl acetate copolymer. Examples of copolymers of ethyleneand octene-1 include Engage products from Dow Chemical such as Engage8480. Typically, this copolymer is used in an amount of from 0 to about90 phr, such as about 10 to about 90 phr, about 10 to about 40 phr, orabout 20 to about 40 phr.

(Additives)

Many different additives may be added to achieve the desired qualitiesof the foam material. These additives are added in an amount to achievethe desired result. For examples, a pigment may added in an amount toobtain the desired whiteness or color of the foam material. Blowingagents are added to achieve the desired density of the foam.

Suitable elastomers can be used including polyoctenylene rubber having ahigh trans content. Such products are available under the trade nameVestanamer from Huls Corp. of West Germany. Particular grades ofVestanamer which are suitable are Vestanamer 8012 and Vestanamer 6213.Such elastomers can be used in a range of about 1 to about 20 phr.

Suitable homogenizing agents can be used, for example mixtures ofaliphatic hydrocarbon resins such as 60 NS by Struktol. Such additivesare added in amounts to provide the desired homogenizing effect andtypically in the range of about 1 to about 3 phr.

Non-reinforcing fillers can be used such as, but not limited to, calciumcarbonate and magnesium carbonate. Such additives are added in amount toobtain the desired effect, typically in a range of about 1 to about 30phr. Suitable pigments can be used such as, but not limited to,Ultramarine Blue. Such pigments are added in amount to obtain thedesired effect, typically in a range of 0 to about 5 phr.

Suitable activators can be used such as, but not limited to zinc oxide.Such activators are added in amount to obtain the desired effect andtypically in a range of 1 to about 5 phr.

Suitable co-agents can be used such as peroxide, SR-350, triallylcyanurate. Such co-agents are added in amount to obtain the desiredeffect and typically in a range of 0 to about 10 phr.

Stearic acid can be used to internal lubricant and activator to obtainthe desired effect and typically in a range of 0 to about 3 phr.

Additives to improve processing characteristics of the foam material maybe used such as polyethylene wax to provide the desired processingcharacteristics and typically in the range of 0 to about 15 phr.

Titanium dioxide can be used along with a pigment in an amount to obtainthe desired effect and typically in the range of 0 to about 20 phr.Anatase or Rutile forms of the titanium dioxide can be used.

Suitable cure system and blowing agents can be used, typically in therange of 0.5 to about 18 phr. Some chemical blowing agents can vary thegas pressures and microcellular cell structure. Suitable chemicalblowing agents include modified or activated azodicarbonamides,dinitrosopentamethylene tetramine, sulfonyl hydrazides.

Suitable polymerization initiators can be used such as peroxides.Polymerization initiators are typically used in the range of about 1 toabout 6 phr. Suitable peroxides include dicumyl peroxide, dibenzoylperoxide and 2,5 dimethyl-2,5-di-(tert-butylperoxy)hexyne-3.

The following provides a table of potential ingredients to prepare thefoam material. In general, the desired polymers/copolymers are combinedwith suitable additives and cure system and blowing agents.

PHR (Parts per hundred) Inventive Foam Range Polymers Alpha OlefinCopolymer  5-40 Hydrogenated acrylonitrile-butadiene, zinc oxide, 15-30zinc diacrylate blend Hydrogenated acrylonitrile-butadiene 10-90Additives Elastomer (Polyoctanamer)  0-20 Homogenizing agent 1-3Non-reinforcing filler  0-10 Activator (Zinc oxide) 0.5-3  Coagent #11-5 Stearic Acid 0-2 Processing Agent (Polyethylene Wax)  0-15 Titaniumdioxide 0-5 Pigment (Ultramarine Blue) 0-1 Cure System and BlowingAgents Blowing Agent #1  1-18 Blowing Agent #2 1-5 Polymerizationinitiator (Dicumyl Peroxide) 2-6 Coagent #2 0.5-2 

The foam can be formed in a suitable manner. For example, the materialscan be mixed together using any suitable mixer such as a Branbury mixer.

Generally, the polymers are loaded first along with a homogenizing agent(if desired) at a temperature of about 30 to 60° C. The polymers arepremasticated for a suitable time, typically about 1 minute and then, ata temperature of about 60 to about 80° C., the remaining ingredients areadded except the cross-linker, peroxide, and blowing agent. Thetemperature is heated to about 80 to about 105° C. while mixing. Thecross-linker is added followed by the peroxide and blowing agent. Thetemperature is raised to 100 to 130° C.

The mixture can be transferred to a pelletizing machine (to formpellets) or to a roll mill (to form sheet stock). For example, in a rollmill, the distance between rollers is 3-4 mm. The mix is homogenized onthe roller for about 3-10 minutes at about 90 to 110° C. and then rolledto the desired thickness.

A pelletizing machine allows the material to be processed usingtraditional EVA or rubber injection machines. The mold temperature inthe pelletizing machine is typically set to about 150 to about 170° C.The resulting product can be stabilized in a cooling tunnel or can beallowed to cool at room temperature.

A roll mill, typically a 2 roll mill, provides a sheet stock inaccordance with conventional techniques. The sheet stock is furtherprocessed using traditional compression molding methods for footwearmanufacturing.

The cure temperature of the foam is typically 150° C. to 170° C. Curetimes and mold thickness are variable depending on the desired thicknessof the foam material. The foam material can be used for the innermidsole core.

The properties of the foam provide the lightweight spongy feel. Thedensity of the foam material is generally less than 0.25 g/cm³, (forexample 0.05 to 0.25 g/cm³), less than 0.20 g/cm³, less than 18 g/cm³,less than 0.15 g/cm³, less than 0.12 g/cm³, and in one aspect, about0.10 g/cm³.

Resiliency of the foam is greater than 40%, greater than 45%, at least50%, and in one aspect from 50-70%. Compression set is 60% or less, (forexample 20 to 60%), 50% or less, 45% or less. The hardness (DurometerAsker C) of the foam is typically, 25 to 50, 25 to 45, 25 to 35, 35 to45, depending on the type of footwear, for example. A running shoetypically has a hardness of 25 to 35 Asker C whereas basketball typeshoes have an Asker C of about 35 to 45 Asker C.

The tensile strength is at least 15 kg/cm², typically 15 to 40. Theelongation % is 150 to 500, typically above 250. The tear strength is6-15 kg/cm, typically above 7.

The foam material has lower energy loss and is more lightweight thantraditional EVA foams. Energy loss is generally less than 30% or about20% to about 30%.

For example, traditional ethylene vinyl acetate (EVA) foams typicallyhave a resilience of 30-40%, a compression set of 50-60%, and a densityof 0.15-0.25 g/cm³.

EXAMPLE 1

The following foam material was prepared using hydrogenatedacrylonitrile-butadiene.

PHR (Parts per Inventive Foam hundred) Polymers Engage 8480 (Copolymerof ethylene & Octene-1) 25 ZSC 2095 (Hydrogenatedacrylonitrile-butadiene, 15 zinc oxide, zinc diacrylate blend) Zetpol2000 (Hydrogenated acrylonitrile-butadiene,) 60 Additives Vestanamer8012 (Polyoctanamer) 10 60 NS (Homogenizing agent) 1 CaCo3 (Filler) 2ZnO (Activator) 0.5 SR350 (Crosslinker) 1 ST-AC (Stearic Acid) 1 AC617(Polyethylene Wax) 7 TiO₂ (Titanium dioxide) 3 Ultramarine Blue 0.4 CureSystem and Blowing Agents Rhenoslab AZ130-75 (Blowing Agent) 12 BlowformSH (Blowing Agent) 2 Akroform DC-40 EPR (Peroxide) 4 TAC-50 (triallylcyanurate) 1 Cure temperature 315 F. Cure time 20 min Mold thickness 10mm Density (g/cm3) 0.11 Appearance Good Process temp 180-220 F. PhysicalProperties A Durometer Asker C 34 Tensile kg./cm² 18, 17, 19 Elongation% 313, 322, 349 Tear kg./cm 8.1, 7.6, 7.6 Split Tear kg./cm. 1.5Shrinkage 2.9 S.G._by Dimension 0.11 Compression set % 20 Resiliency 52

EXAMPLE 2

The following foam material was prepared using non-hydrogenatedacrylonitrile-butadiene.

PHR (Parts per Inventive Foam hundred) Polymers Engage 8440 (Copolymerof ethylene & Octene-1) 35 ZSC 2095 (Hydrogenatedacrylonitrile-butadiene, 15 zinc oxide, zinc diacrylate blend) NipolDN1201L (Acrylonitrile-butadiene) 50 Additives Vestanamer 8012(Polyoctanamer) 10 60 NS (Homogenizing agent) 1 CaCo3 (Filler) 7 ZnO(Activator) 1 SR350 (Crosslinker) 2 ST-AC (Stearic Acid) 1 TiO₂(Titanium dioxide) 7 Ultramarine Blue 1 Cure System and Blowing AgentsRhenoslab AZ130-75 (Blowing Agent) 13 Akroform DC-40 EPR (Peroxide) 4Cure temperature 315 F. Cure time 10-12 min Mold thickness 6 mm Density(g/cm3) 0.1 Physical Properties A Durometer Asker C 24 Tensile kg./cm²9.4, 8.7, 8.8, 10.7 Elongation % 150, 143, 148, 182 Tear kg./cm 4.4,4.5, 4.8, 4.7 Split Tear kg./cm. 0.51 Shrinkage 5.4, 4.8 S.G._byDimension 0.09, 0.09 Compression set % 67, 71

EXAMPLE 3

A study was conducted to compare the steady state energy expenditurewhen wearing Nike Air Pegasus and Nike Lunar shoes made in accordancewith the invention. The weight of the Lunar shoes was less than half theweight of the Pegasus shoes as shown in the following table

Weight Shoe Per shoe Lunar: Men 135 g Pegasus: Men 322 g Lunar: Women126 g Pegasus: Women 312 g

Twenty-two (10 male and 12 female) well-conditioned runners wereprovided with both Nike Air Pegasus and Nike Lunar shoes. Male subjects:Age 26.9±7.2 years, weight 65.8±6.4 kg. Female subjects: Age 29.0+10.2years, weight 57.3±4.8 kg. The subjects were dressed in their normalrunning shirts and shorts. All subjects wore the same Nike short-cutDri-Fit socks (14 g each).

The environmental chamber was set at 20° C.; 50% RH. Airflow at aconstant 2.5 m/sec was directed toward the front of the subject; otherbody surfaces were exposed to turbulent airflow at rates ≦1.4 m/sec.Shoes were assigned in counter-balanced order and each subject completedfour consecutive 10-minute bouts of exercise, alternating shoes duringthe 3-minute break between runs, thus wearing each shoe twice during thetest session. Level treadmill running speeds averaging 8.1 and 8.6 mphfor the females and males, respectively, were set to requireapproximately 80% of each subject's aerobic capacity.

Heart rate was monitored continuously (Polar, Inc.) and recorded everyminute. Oxygen consumption was monitored continuously (ParvoMedics, Inc)and the mean of the last four minutes (e.g., minutes 7 thru 10) wasselected as the most valid estimate of the steady-state energyexpenditure during each experiment. Hence, the data reported for eachsubject represent the mean for duplicate experiments for each shoeduring the same testing session. Pre- and post nude weights weremeasured on a scale accurate to ±10 g (Ohaus Corp).

Heart rates (bpm) were calculated as percent of predicted heart ratemax. Steady-state values for oxygen consumption were calculated asml/kg·min⁻¹.

Twenty of the 22 subjects exhibited a lower oxygen requirement whenwearing the lighter Lunar shoe. These reductions in energy expenditurewhen running at the same pace on a level treadmill were significant(P<0.01) and averaged −3.0±1.0% and −3.5±1.9% for the male and femalesubjects respectively.

Steady state heart rates for the males averaged 79% and 80% of theirage-predicted maximal values when wearing the Lunar and Pegasus shoes,respectively. Corresponding values for the female subjects were 85% and86% of their age-predicted maximal heart rates.

When queried, the subjects preferred the Lunar shoe for running underthese conditions.

EXAMPLE 4

Comparative values were obtained for Peak G, Energy Absorption, and CDCurves for the following types of cores and core/shell combinations:

-   -   A. CMP LUNAR FOAM CORE Made in WHQ (M4533 A)    -   B. CMP EVA PHYLON FOAM CORE Made in WHQ (M4533 B)    -   C. INJECTED LUNAR FOAM CORE Made in Asia (FT) (M4533 C)    -   D. CMP LUNAR CORE (WHQ), ASSEMBLED WITH PHYLON SHELL (M4532 A)    -   E. INJECTED LUNAR CORE (ASIA FT), ASSEMBLED WITH PHYLITE SHELL        (M4532 B)

Sample 1 foam formula were used in A and C above. The injected and CMPcores have the same formula except they were processed by differentmethods.

Thickness Peak Energy ID Sample (mm) G Loss (%) A M4533 - A1 Heel 17.914.4 26 B M4533 - B1 Heel 17.9 11.1 36 C M4533 - C1 Heel 23.1 10.1 29 DM4532 - D1 Heel 29.3 8.2 37 E M4532 - E1 Heel 29.4 9.0 36 A M4533 - A1FF 11.2 38.6 27 B M4533 - B1 FF 10.5 29.8 32 C M4533 - C1 FF 13.0 29.528 D M4532 - D1 FF 20.5 13.8 31 E M4532 - E1 FF 21.1 12.8 37

Results for heel and forefoot impact results are shown in FIGS. 5a, 5b ,5 c, 5 d, 5 e, and 5 f. FIG. 5a depicts heel impact G results. FIG. 5bdepicts heel impact energy loss results. FIG. 5c depicts forefoot impactG results. FIG. 5d depicts Forefoot impact energy loss results.

Results for M4533 Samples A, B and C

For a heel impact, the results of FIG. 5a indicate that Sample C had thelowest Peak G with a value of 10.1 G, followed by sample B with a Peak Gof 11.1 G and Sample A with the highest Peak G and a value of 14.4. ForEnergy Loss values shown in FIG. 5b , Sample A had the lowest with avalue of 26%, Sample C had the next lowest with value of 29% and SampleB had the highest with 36%.

For a forefoot impact, the results shown in FIG. 5c indicate thatSamples B and C had the lowest Peak G ranging from 29.5 to 29.8 G.Sample A had the highest value of 38.6 G. For Energy Loss values shownin FIG. 5d , the samples ranged from 28 to 32%, which was not consideredto be meaningful differences.

Load vs Deflection curves are depicted in FIG. 5e and FIG. 5f for heelimpact Peak G results and forefoot impact G results, respectfully. Thesharp spikes in the curves for sample A, B, and C indicate that thesamples were starting to bottom out.

Results for M4532 Samples D and F

For heel impact, the results in FIG. 5a indicate that Sample D had thelower Peak G with a value of 8.2 G compared to Sample E with a value of9.0 G. The Energy loss values in FIG. 5b range from 36 to 37% which wasnot considered a meaningful difference.

For a forefoot impact, the results in FIG. 5c indicate Sample E has thelower Peak G with a value of 12.8 G compared to Sample D with a value of13.8 G. The Energy loss values in FIG. 5d range from 31 to 37% which isnot considered to be a meaningful difference.

Generally speaking, a lower Peak G value indicates softer cushioning, ahigher value indicates firmer cushioning. A difference in Peak G valuesgreater than 0.5 G is considered to be a meaningful difference (outsidethe variance of the machine.) A difference in Peak G values greater than1.0 G for a heel impact indicates that to a discerning consumer, a “JustNoticeable Difference” (JND) may exist between the two shoes. EnergyLoss is a measure of responsiveness, the lower the Energy Loss the moreresponsive the cushioning. A difference in Energy Loss greater than 10%is considered to be a meaningful difference.

In light of the foregoing disclosure of the invention and description ofvarious embodiments, those skilled in this area of technology willreadily understand that various modifications and adaptations can bemade without departing from the scope and spirit of the invention. Allsuch modifications and adaptations are intended to be covered by thefollowing claims.

What is claimed is:
 1. A sole assembly for an article of footwear, theassembly comprising: a first portion having a lower ground engagingsurface, an upper surface, and a recess formed in the upper surface; anda second portion seated in the recess in the first portion and having anupper surface, wherein the second portion is formed from a first foammaterial comprising a reaction product of a composition comprising about10 to about 100 phr of a hydrogenated copolymer and about 10 to about 90phr of a copolymer of ethlylene and an alpha olefin, the alpha olefinhaving up to 20 carbon atoms, the first foam material having a hardnessof 25 to 45 Asker C and a density of less than 0.18 g/cm³.
 2. The soleassembly of claim 1, wherein the composition comprises about 30 to about90 phr of the hydrogenated copolymer.
 3. The sole assembly of claim 1,wherein the composition comprises about 20 to about 40 phr of thecopolymer of ethylene and the alpha olefin.
 4. The sole assembly ofclaim 1, wherein the alpha olefin is an alpha olefin having 3 to 20carbon atoms.
 5. The sole assembly of claim 4, wherein the alpha olefinis 1-octene.
 6. The sole assembly of claim 1, wherein the hydrogenatedcopolymer comprises a hydrogenated copolymer including butadiene units.7. The sole assembly of claim 6, wherein the hydrogenated copolymercomprises a hydrogenated acrylonitrile butadiene copolymer.
 8. The soleassembly of claim 1, wherein the composition further comprises across-linker, a peroxide, a blowing agent, and combinations thereof. 9.The sole assembly of claim 1, wherein the density of the first foammaterial is less than 0.15 g/cm³.
 10. The sole assembly of claim 1,wherein the density of the first foam material is less than 0.12 g/cm³.11. The sole assembly of claim 1, wherein the hardness of the first foammaterial is 25 to 35 Asker C.
 12. The sole assembly of claim 1, whereinthe hardness of the first foam material is 35 to 45 Asker C.
 13. Thesole assembly of claim 1, wherein the first foam material has acompression set less than 50% and a resiliency greater than 40%.
 14. Thesole assembly of claim 1, wherein a density of the first portion isgreater than 0.18 g/cm³.
 15. The sole assembly of claim 1, wherein thefirst portion comprises a heel portion, a midfoot portion, and aforefoot portion.
 16. The sole assembly of claim 15, wherein the recessof the first portion extends from a rear of the heel portion to a frontof the forefoot portion.
 17. The sole assembly of claim 1, wherein thesole assembly further comprises a second foam material, the second foammaterial having a density greater than or equal to 0.25 g/cm³.
 18. Thesole assembly of claim 17, wherein the second foam material is locatedin the heel region of the recess.
 19. The sole assembly of claim 1,wherein the sole assembly further comprises at least one rib extendingsubstantially horizontally along a sidewall of the sole assembly. 20.The sole assembly of claim 8, wherein the at least one rib extendsoutwardly from the first portion.